This invention relates to a method for producing sulfur from sulfur dioxide. More particularly, this invention relates to a process for the production of sulfur from sulfur dioxide wherein a lower monohydric alcohol is employed as a reducing agent. As is well known, sulfur dioxide is a most undesirable pollutant emitted to the atmosphere as a component in a large number of process, flue gas and/or combustion gas streams conventionally vented to the atmosphere. As is also well known, considerable effort has been expended in recent years to develop both an effective and economical process for separating sulfur dioxide from such streams. Mere separation from these gas streams is, however, not enough since the SO.sub.2, in a gaseous state, cannot be conveniently stored or disposed of. As a result, it has become necessary to convert the SO.sub.2 to a non-pollutant form which itself can be either easily stored or productively used.
One such conversion is accomplished by reducing the sulfur dioxide to either sulfur and oxygen or to sulfur and water and, heretofore, several processes have been proposed for this purpose. Generally, these processes involve the use of either a gaseous or solid reducing agent and some have been found quite effective for this purpose. In this regard, it should be noted that those processes using a non-carbonaceous reducing agent such as hydrogen generally lead to the production of a high quality sulfur which can be sold commercially and used for any of the purposes for which sulfur is normally employed. The principal problem associating with these processes, however, is that hydrogen is not generally readily available at those sites where sulfur dioxide is conventionally vented to the atmosphere. Moreover hydrogen cannot be conveniently shipped and stored at these sites due primarily to the large shipping and storage capacities which would be required and/or the pressurized equipment which would be necessary therefor. As a result, if hydrogen were to be used to produce sulfur from the sulfur dioxide normally vented to the atmosphere, the same would, generally, be prepared at the site from another material, such as methane, LPG or the like, which is more conveniently available at the side. The problem with this approach is, of course, that an increased captial investment would be required to effectively separate the normally vented sulfur dioxide and, since an additional operating step would be required for such separation, the continuing operating cost would be increased.
Other sulfur producing processes, on the other hand, and particularly those employing a carbonaceous reducing agent, such as methane, LPG or the like, do not, generally, yield a high purity sulfur which would be useful in those areas wherein sulfur is normally employed. In this regard, it should be noted that the use of a carbonaceous reducing agent is, generally, accompanied with an undesirable tendency to form soot, carbon oxysulfide and carbon disulfide as by-products of the reducing reaction. These products are, of course, undesirable in that all will, to some extent, adversely affect the purity of the more desirable sulfur product or products. Moreover, soot will, generally, discolor the elemental sulfur product, while carbon disulfide, which is not easily converted to elemental sulfur, will decrease the yield thereof.
In light of the deficiencies associated with the prior art processes, it is believed that the need for an improved process which employs a reducing agent which is either readily available or easily stored at the site and which will yield a high purity sulfur product which can be sold commercially and used in those areas where sulfur is normally employed is believed to be readily apparent.